1. Field of the Invention
The present invention relates to audio systems and, more particularly, to customizing personal audio systems for hearing impaired individuals.
2. Description of the Related Art
One out of ten people suffer from some degree of hearing loss. However, due to stigma, cost, and availability only about 20% of those who have hearing loss wear hearing aids. In contrast, most people have a telephone and many people have mobile phones (e.g., cellular phones). About 70% of people in the United States have a mobile telephone. Currently, mobile phones are only intended for the normal hearing population and cannot be used by hearing impaired individuals who do not use hearing aids. Thus, the majority of the hearing impaired population lives regrettably without use of a mobile phone.
Since the degree of hearing loss varies from person to person, the amplification requirement for each hearing-impaired individual can be significantly different. Special expertise is required in order to customize a mobile phone for a specific hearing-impaired individual. What makes this situation more difficult is that most hearing impaired people have never visited a hearing specialist and do not have any information about their hearing loss, making it impossible to customize mobile phones and other telephone systems for them.
In most developed countries, hearing loss is diagnosed using specialized equipment known as an audiometer. Typically, a patient must visit a hearing specialist's office or an ear, nose and throat (ENT) doctor's office to have hearing loss testing performed. If hearing loss is diagnosed, the hearing specialist or doctor will counsel the patient to consider using a hearing aid. If the patient chooses to purchase a hearing aid, the hearing specialist or doctor has to spend additional time fitting the hearing aid to the patient. All these services are expensive and usually not covered by health insurance or the government.
As noted above, conventional hearing loss testing is performed using an audiometer. The audiometer presents a calibrated pure tone signal to the patient via a transducer, such as a headphone, an earphone or a loudspeaker to one of the patient's ears. If the patient hears the tone, the level of the tone will be reduced and presented to the patient again. If the patient cannot hear the tone, the level of the tone will be increased and presented to patient again. This procedure is repeated many times until a certain number of reversals from decreasing the tone to increasing the tone have been reached. The hearing threshold of the patient is defined as the signal level at which the patient can hear the tone 50 percent (50%) of the time the tone is presented to the patient. The hearing threshold can be derived from the various reversal levels. For each ear, the above procedure is usually repeated at 125, 250, 500, 1000, 2000, 4000, and 8000 Hz. If the difference of the hearing thresholds at two adjacent frequencies exceeds a critical value (e.g., 20 dB), an additional test can be performed at a middle frequency. Often, middle frequencies are only applied when needed for frequencies between 500 to 8000 Hz. Accordingly, the maximum number of testing frequencies is usually eleven (e.g., 125, 250, 500, 750, 1000, 1500, 2000, 3000, 4000, 6000, and 8000 Hz).
In order for the hearing loss test results to be meaningful, the testing system (namely, the audiometer) must be calibrated. In other words, the relationship between the electrical settings in the system and the acoustical pressure delivered to the patients (subjects) must be known. Various components affect the calibration including, but not limited to, an electrical system that generates the stimuli and a listening system (transducer) that converts the electrical signal into acoustic pressure. Calibration is further complicated by the fact that sound levels measured at the eardrum of a human varies from person to person, even when delivered with the same system and identical settings. As a result, calibration of a testing system is often conventionally done using a special coupler for which a reference hearing level of normal listeners has been established. For example, the audiometer with an insertion earphone is usually calibrated in a 2 cubic-centimeters (cc) coupler. When listeners with normal hearing listen to pure tones through an insertion earphone, the sound levels (as measured in the 2 cc coupler) of the pure tones need to be set to the following levels (given in Sound Pressure Level (SPL)) for the sounds to be just audible:
FrequencyLevel(Hz)(dB SPL)125452503550020750151000101500820007300012400020600027800030
The above levels are normal reference levels for the insertion earphone in the 2 cc coupler. The reference levels vary for different transducers as well as for different couplers.
Hearing thresholds for a patient are usually expressed in decibels hearing level (dB HL), which is a relative level in reference to the normal reference levels. The reference levels should have been established for the system and transducer used in the test. For example, the normal reference level for an insertion earphone is 7 dB SPL at 2000 Hz as measured in a 2 cc coupler. If the hearing level for a patient is 47 dB SPL at the same frequency as measured in the same 2 cc coupler, the hearing loss for the patient is 40 dB HL. For most commercial audiometers, the normal reference levels can be built into the machine, and the signal level presented to the patient is automatically expressed in dB HL.
Accordingly, there are various problems associated with conventional hearing loss testing. One problem with conventional hearing loss testing is that specialized testing equipment must be used and must be calibrated. Another problem with conventional hearing loss testing is the cost and often limited availability of hearing specialists or ENT doctors to administer the hearing loss examination. As a result, for various reasons, hearing loss testing and hearing loss assistance products are generally not readily available to people.
Thus, there is a need for improved approaches to evaluating hearing loss and assisting those with hearing loss to obtain hearing assistance products or services.